The signatures of Adam Lanza (upper left above the 2) and his fifth-grade classmates appear on a Sandy Hook Elementary T-shirt made by the school and given to each student. / USA TODAY

by Gary Stoller and Oren Dorell, USA TODAY

by Gary Stoller and Oren Dorell, USA TODAY

NEWTOWN, Conn. -- The gunman who killed 20 elementary school students in their classrooms had once attended the same school, according to a school administrator and a former classmate.

Superintendent Janet Robinson said Adam Lanza attended Sandy Hook elementary, although she could not remember the year.

"I know that he was a student at Sandy Hook at some point," she said.

Investigators have said nothing about a possible motive or why Lanza targeted the school.

Relatives have denied that Lanza attended the school. But at least one former classmate said that he apparently attended the school in fifth grade in fall 2002.

Lanza, 20, killed 20 children and six adults and wounded two others at the school Friday morning. Earlier, he had shot and killed his mother at their home. He fatally shot himself after the attacks.

The signatures of Lanza and his fifth-grade classmates are on a Sandy Hook Elementary T-shirt made by the school and given to each student. Lanza and other fifth graders attended the school in fall 2002.

The Sandy Hook School T-shirt says "2003," but Lanza and his classmates actually left Sandy Hook at the end of 2002. In January 2003, they moved to newly built Reed Intermediate School for fifth- and sixth-graders.

Lanza was home-schooled for some of his education, family members have said.

Fifth-grade classmate Dan Lynch, now a junior at the University of Connecticut, remembers Lanza at Sandy Hook Elementary.

"I was in class with him in fifth grade, and he was extremely introverted," Lynch says. "He was really skittish, always anxious and nervous."

Lynch says he remembers watching a sex-education movie, and Lanza saying he was about to throw up and needed to leave the room.

Lynch says Lanza was "a nice kid when he did talk to you," and "not a bad person."

Lanza "kept to himself, and everyone left him alone," Lynch says. "I can never recall him getting bullied."

Details of the drama surrounding the school continued to surface. One firefighter in the initial rescue squad to respond to the 911 call last week at Sandy Hook Elementary had a son in the school at the time of the shooting, Sandy Hook Fire Chief William Halstead told Fire Chief magazine in an interview published Tuesday.

Halstead's daughter, Karin Halstead, the EMS captain, spotted the boy, who was safe. The wife of another firefighter was visiting the school and hid behind a dumpster during the shooting, Halstead said.

Halstead told the magazine that the firefighters set up a triage area, expecting dozens of wounded people, but cared for only two victims: one woman with gunshot wounds in her hand and thigh and one woman with gunshot wounds in her leg and foot.

Halstead said his ex-wife and the school nurse hid in a closet when the shooting started.